Air conditioning apparatus

ABSTRACT

Apparatus for supplying treated air to an enclosure including a heat exchanger through which a heat exchange medium flows and a fan arranged to route air to be treated over the heat exchanger in heat transfer relation with the medium. A supply duct, including one or more damper assemblies provided to regulate the discharge of treated air from the system, delivers the treated air to the enclosure. The position of the damper assemblies is modulated in response to the temperature of the air in the enclosure. A pressure responsive element operates to sense the variations in pressure in the supply duct produced by the modulation of the damper assemblies and creates a control signal which operates to vary the speed of the fan in response to the changes in pressure to maintain the pressure in the duct substantially constant.

O United States Patent 1151 3,653,590 Elsea 1 Apr. 4, 1972 [54] AIRCONDITIONING APPARATUS Primary Examiner-Edward J. Michael [72] InventorRflph Elsa, Syracuse, NY Attorney-Harry 6. Martin, Jr. and 1. RaymondCurtin [73] Assignee: Carrier Corporation, Syracuse, NY. ABSTRACT 22]Fil d; J l 27, 1970 Apparatus for supplying treated air to an enclosureincluding a heat exchanger through which a heat exchange medium flows[2H APPI- NW 58,313 and a fan arranged to route air to be treated overthe heat exchanger in heat transfer relation with the medium. A supply[52] "an/4933mm duct, including one or more damper assemblies providedto [51] In CL I um 7/00 regulate the discharge of treated air from thesystem, delivers 58 Field of Search ..236/l B 1 1 as treated The damp" Isemblies is modulated in response to the temperature of the [56]References Cited air in the enclosure. A pressure responsive elementoperates to sense the variations in pressure in the supply duct producedUMTED STATES N S by the modulation of the damper assemblies and createsa control signal which operates to vary the speed of the fan in2,223,287 1 1/1940 Kmgsland ..236/l B response to the changes inpressure maintain the measure in 3,486,693 12/ 1969 Stang et al...236/ll X the duct substantially constant- 3,489,345 11/1970 'Moreland..236/il X 1 Claim, 2 Drawing Figures Patented April 4, 1972 ON E T 8 8ATTORNEY AIR CONDITIONING APPARATUS BACKGROUND OF THE INVENTION Thisinvention relates to air conditioning apparatus and, more particularly,to an arrangement for controlling the discharge of treated air from saidapparatus.

Air conditioning apparatus of the type employing a heat exchange coil tocirculate a heat exchange medium therethrough, for example, chilled orwarmed water, and having a fan for bringing air to be conditioned intoheat exchange relation with the medium flowing through the coil are wellknown and widely employed by those skilled in the air conditioning art.Such apparatus are generally referred to as fan coil units.

Fan coil units are employed with central station cooling and heatingmachinery for conditioning multi-room buildings, such as motels, hotels,and apartments. Such apparatus afford a relatively effective means forsimultaneously conditioning a plurality of areas in a common enclosure,while providing individual control by the occupants of each area. Inaddition, fan coil units are relatively simple to install and tomaintain tin operating condition and are relatively inexpensive, makingsuch units particularly suitable for low-cost multiple dwelling housing.However, some problems have been encountered which reduce the overallefficiency and effectiveness of their operation.

For example, the on-off cycling of the typical fan coil unit createsannoying sound variances. In addition, an on-off type of control doesnot provide uniform air distribution. Particularly, temperaturevariations of a considerable magnitude above and below the room setpointmay be produced in portions of the room, the variations being caused bystratification of the air during the offcycle.

To overcome these problems, a variable speed control for the fan motor,to modulate the discharge of conditioned air from the apparatus, hasbeen considered.

The variable fan speed control obviates the noise problem bycontinuously operating the fan at the lowest speed consistent with thecooling or heating load thereon. However, at low fan speeds, problemshave resulted due to the low velocity of the conditioned air beingdischarged into the conditioned space, particularly when the air is at arelatively cold temperature. Such low velocity causes the air stream tolose momentum, resulting in the relatively cold air spilling into therooms, rather than following a trajectory above the occupied space untilmixing is complete, thus causing discomfort to the occupants byproducing wide variations in temperature across the room and from floorto head level.

Furthermore, it has been determined that a more efficient control of thehumidity level, when the apparatus is operating on cooling mode, may beobtained by continuously operating the fan rather than employing anon-off cycle of fan operation or modulating the cold water flow to theheat exchange coil.

The object of this invention is an improved air conditioning apparatusemploying a novel arrangement for controlling the flow of treated air tothe enclosure which is compatible with a variable speed control for thefan motor.

SUMMARY OF THE INVENTION This invention relates to air conditioningapparatus, and more particularly to an improved arrangement forcontrolling the flow of treated air from such apparatus.

The apparatus includes a heat exchanger adapted to receive a heatexchange medium, such as chilled or warmed water, which may be treatedin a central station or other remote location. A fan is operable toroute air to be treated over said heat exchange coil in heat transferrelation with the medium flowing therethrough. The treated air from theheat exchange medium is supplied through an air passage to one or moreoutlets.

A temperature sensing element is installed in the area being treated andis operable to generate a signal, the magnitude thereof being related tothe sensed temperature in the treated area. The signal is supplied tomeans operable to vary the size of the discharge area of the outlet toprovide a quantity of treated air in proportion to load requirements ofthe area.

By modulating the area of the discharge outlet, the pressure in thesupply air passage is varied in proportion thereto. A pressure sensingelement is disposed in the air passage to sense the variations ofpressure therein. of pressure therein. The pressure responsive elementgenerates a signal which is proportional to the sensed temperature andsupplies said signal to the fan motor control circuit. The speed of thefan is thereby modulated to maintain a predetermined static pressure inthe air passage regardless of the area of the discharge outlet. Bymaintaining the static pressure substantially constant, the dischargevelocity will also be maintained substantially constant, therebyobviating the problems hereinbefore discussed.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic view of a fancoil unit of the type described equipped with a control circuitillustrating the invention; and

FIG. 2 is a schematic diagram illustrating the circuit used to convertconventional AC voltage to DC voltage to provide a source of power forthe circuit illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, thereis shown a preferred embodiment of air conditioning apparatus includingthe invention disclosed herein.

Reference numeral 10 indicates an area or an enclosure which is to betreated by having air at a predetermined temperature discharged therein.Although it is within the scope of the invention to have only one sucharea or room being conditioned, it should be understood several rooms,each employing apparatus embodying the subject of this invention, may beconditioned simultaneously.

The illustrated embodiment includes air conditioning apparatus 12.Apparatus 12 includes a heat exchange coil 13 to which a heat exchangemedium, such as cold or warm water, is supplied via conduit 14. The heatexchange medium is supplied at a predetermined temperature which isregulated by central station refrigeration machinery (not shown). Theheat exchange medium is returned to the central station machinery viaconduit 15. Fan 16 operatively connected to an electric motor routesambient air over the heat exchange coil in heat transfer relationtherewith; The ambient air is treated by passing in heat transferrelation with the heat exchange medium flowing through the coil.

The air conditioning apparatus 12 is mounted in a structure or casing 17which defines an air passage through which the treated air is suppliedto at least one outlet 18 for delivery to the room or enclosure beingtreated. Damper 19 regulates the passage of air to the enclosure fromoutlet 18. The manner in which damper 19 is controlled in accordancewith the invention disclosed herein shall be more fully explainedhereinafter.

As noted hereinbefore, it is desirable to regulate the quantity oftreated air being supplied to the enclosure in accordance with the loadrequirements thereof. By regulating the position of damper 19 to varythe discharge area from outlet 18, it is possible to modulate the supplyof treated air as is desired by varying the speed of fan 16, therebyeliminating the prior art difficulties noted hereinbefore.

The novel arrangement herein disclosed operates to maintain the velocityof the treated air discharged into the enclosure substantially constantregardless of the quantity of air being supplied. Any desirable velocitylevel, within the capability of the fan, may be selected, either byadjustment or design, to be compatible with the requirements of thespace.

The control circuit provided for obtaining the desirable featureshereinbefore described is merely illustrative, and other control schemesthat might perform a similar function may be employed in lieu thereof.

The control circuit includes a voltage transformer operable to reducethe line voltage represented by lines L and L to a smaller voltage forcontrol purposes. The voltage transformer includes a primary winding 20and a secondary winding 21. Preferably, the current flowing throughlines L and L is 60 cycle alternating current. Since the controlcircuit, to be more fully explained herein, utilizes solid statecomponents operable on direct current, a full wave diode rectifiercircuit 22 is provided as a source of DC voltage, the DC voltage sourcebeing represented by +E, abd E,. Resistors 66 and 67 and capacitors 68and 69 are provided to filter the DC voltage signal.

Thermostat elements 23 and 24 are connected in series with the source ofDC voltage. Element 24 is preferably a variable resistance element, suchas a potentiometer, that may be selectively regulated by the occupant toobtain a desired temperature in the enclosure. Element 23 is preferablya NTC thermistor positioned to sense the temperature of the air in theenclosure. Elements 23 and 24 operate in combination to provide avariable voltage signal. When the temperature of the enclosure is abovethe setpoint established by thermal element 24, the voltage signal is ofa relatively large magnitude and of a positive polarity, whereas whenthe temperature is below the setpoint, the voltage is of a relativelylarge magnitude and of a negative polarity.

The voltage signal from elements 23 and 24 is supplied to a first inputof operational amplifier 26 through resistor 25. The manner in whichoperational amplifier 26 functions shall be more fully explainedhereinafter. Operational amplifier 26 also has supplied thereto a +E,voltage through line 70 and a -E, voltage through line 71.

Connected to the output of the operational amplifier is a first diode 27and a second diode 28. Diode 28 permits only passage of a negativevoltage signal, whereas diode 27 only permits passage of a positivevoltage signal.

Connected in series with diode 27 is relay coil 32, the energizationthereof operating to close normally open switch 33. Connected in serieswith diode 28 is relay coil 30, the energization thereof operating toclose normally open switch 31.

Connected to the output from either switch 31 or switch 33 isdouble-pole, double throw switch 34. Switch 34 includes a first pole 39which selectively connects either terminal 37 or terminal 38 in thecircuit. Terminal 37 is connected into the circuit when the apparatus isproviding relatively cold air, whereas terminal 38 is connected in thecircuit when the apparatus is providing relatively warm air. Switch 34also includes pole 40 which selectively places either terminal 35 orterminal 36 into the circuit. Terminal 35 is placed in the circuit whenthe apparatus is providing relatively cold air, and terminal 36 isplaced in the circuit when the apparatus is providing relatively warmair.

Switch 34 may be controlled manually or may be operated automatically bymeans such as a bimetal switch which would be placed in heat transferrelation with the heat exchange medium flowing to heat exchange coil 13.

Connected in series with switch 34 are windings 41 and 42 of reversiblemotor 43, having line voltage supplied thereto via lines L, and L Theenergization of winding 41, prior to the energization of winding 42,will actuate the motor so that the damper will rotate in acounterclockwise direction so that the discharge area of outlet 18 isincreased.

Conversely, the energization of winding 42, prior to the energization ofwinding 41, will actuate motor 43 so that damper 19 will rotate in aclockwise direction to decrease the discharge area from outlet 18. Motor43 is operatively connected to damper 19 via shaft 44. Capacitor 65 isincluded between windings 41 and 42 to establish the necessary phasedisplacement therebetween.

Operatively connected to shaft 44 is shaft 47. Shaft 47 has movablyconnected thereto wiper 46 of potentiometer 45. The rotation of shaft 44so as to decrease the area of discharge outlet 18 will rotate wiper 46in a clockwise direction, whereas rotation of shaft 44 so as to increasethe area of discharge outlet 18 will rotate wiper 46 in acounterclockwise direction.

Connected in series with potentiometer 45 is a second double-pole,double throw switch 50. Switch 50 includes arm 51 and arm 52. As shownby the solid line, arms 51 and 52 are positioned for cooling modeoperation. As shown by the dotted lines of the Figure, 51 and 52 arepositioned for heating mode operation. The operation of switch 50 may bemanually or automatically regulated.

Connected in series with switch 50 and potentiometer 45 are fixedresistors 48 and 49. Lines 76 and 77 are connected to the source ofrectified DC voltage so as to bring the supply voltage to potentiometer45.

Depending upon the mode of operation and the position of wiper 46 asdetermined by the position of damper 19, either a positive polarity or anegative polarity voltage signal will be supplied via line 72 andresistor 54 to a second input of operational amplifier 26, the signalbeing proportional to the position of the damper.

The operational amplifier compares the voltage signal regulated bypotentiometer 45 to the voltage signal regulated by thermal elements 23and 24 to operate motor 43 so that the position of damper 19 ismodulated in response to the temperature of the enclosure.

Positioned in the air passage defined by structure 17 is a pressuresensing device 63. As the position of damper 19 is varied, the staticpressure in the air passage will be simultaneously varied. Device 63 ispositioned so as to sense the variations in pressure caused by themovement of damper 19.

Device 63 includes arm 64 mounted to pivot about fulcrum 61. Connectedto one end of arm 64 is wiper 62 of potentiometer 60. Wiper 62 isconnected to arm 64 so that as the static pressure in the air passageincreases, the wiper rotates so as to increase the resistance presentedby potentiometer 60. Conversely, as the static pressure in the airpassage decreases, wiper 62 will rotate about pivot 61 so as to decreasethe resistance presented by potentiometer 60.

Connected in series with one terminal of the potentiometer 60 is triggerdiode 55 sold under the trademark Diac." Connected to one side of thesource of alternating current represented by line L is capacitor 57. Theother side of capacitor 57 is connected to form a junction with one sideof trigger diode 55. Connected to the second side of diode 55 is thegate 56' of a bi-directional gated solid state switch 56 of a type soldunder the trademark Triac.

Switch 56 is triggered to a conducting state by either a positive or anegative pulse being applied to gate 56. Switch 56 should besufficiently fast in operating so it may be switched on during anydesired portion of each half-cycle of alternating current supplied tothe motor driving fan 16 to arrive at a desired average power. The motorspeed and the fan speed are thus varied in accordance with the capacitydemand of the room served by the system.

To better understand the manner in which the control circuit operates inaccordance with the invention, assume that cooling mode operation isdesired and that the temperature of the enclosure is above the setpointThe magnitude of the variable voltage control signal controlled bythermal elements 23 and 24 will be sufficient to cause operationalamplifier 26 to pass a positive polarity voltage signal from line 70 toline 29.

The +E, voltage signal will pass through diode 27 and energize coil 32,thereby closing switch 33.

Upon closure of switch 33, line voltage represented by L and L will passthrough arm 39 of double-pole, double-throw switch 34 which is incontact with terminal 37 to first energize coil 41 of motor 43. Themotor will thus be actuated to turn shaft 44 in a counterclockwisedirection to open damper 19.

As damper 19 moves in a counterclockwise direction wiper 46 ofpotentiometer 45 simultaneously moves in the same direction, theposition thereof being related to the position of the damper.Double-pole, double-throw switch 50 is set for cooling mode operation.Therefore, arm 52 is in a position in which the +E, control signal willpass through resistor 49 and wiper 46 to line 72, the magnitude of thesignal being proportional to the position of the damper. When theposition of the damper has reached an equilibrium point in relation tothe temperature of the enclosure, the magnitude of the control signal inline 72, as determined by the position of wiper 46, will be equal to themagnitude of the variable voltage control signal regulated by thermalelements 23 and 24 and will thus place operational amplifier 26 in anonconducting state, turning off motor 43.

As damper 19 moves in a counterclockwise direction, the static pressurein the air passage decreases. Wiper 62 will move in a direction so as todecrease the resistance presented by potentiometer 60, therebyincreasing the rate at which capacitor 57 is charged. When the charge oncapacitor 57 reaches a predetermined value, the trigger diode 55 will beplaced in a conducting state, thereby passing a pulse to a gate 56 ofswitch 56. When switch 56 is placed in its conducting state, currentwill flow to the motor driving fan 16 at an increased rate to increasethe speed thereof. Thus, it is apparent that as the position of thedamper is moved in a counterclockwise direction to increase the area ofthe discharge opening, the static pressure in the air passage isdecreased; and simultaneously therewith, the speed of the fan isincreased, thereby increasing the flow of air through the air passage toincrease the static pressure to its desired predetermined point. By thusmaintaining the static pressure substantially constant, the velocity ofthe air being discharged will also remain substantially constant toobviate the problems hereinbefore discussed.

if the temperature of the enclosure has fallen below the setpoint duringcooling mode operation, the magnitude of the variable voltage controlsignal supplied to operational amplifier 26 will be such that a negativepolarity control signal will pass from line 71 to line 29. i

The E, control signal will pass through diode 28, thereby energizingrelay coil 30, thus closing switch 31.

When switch 31 closes, line voltage will pass to terminal 35 ofdouble-pole, double-throw switch 34 and will flow through arm 40 to coil42, thus energizing motor 43 to cause shaft 44 to rotate in a clockwisedirection.

Wiper 46 of potentiometer 45 will simultaneously move in a clockwisedirection. Arm 51 of double-pole, double-throw switch 50 will provide a-E, voltage signal through line 76 and resistor 48 to the wiper. Themagnitude of the voltage signal will be determined by the position ofthe wiper relative to the resistance elements of potentiometer 45. Thevariable voltage signal will then flow through line 72 to resistor 54and operational amplifier 26. When the magnitude thereof is equal to themagnitude of the variable control signal regulated by thermal elements23 and 24, operational amplifier 26 will become nonconductive.

Simultaneously, as the damper is moved in a clockwise direction, wiper62 of potentiometer 60 moves in a direction to increase the resistancethereof due to the reduction of the static pressure in the air passage.

As the resistance of the potentiometer is increased, the rate at whichcapacitor 57 is charged is decreased, thereby delaying the time duringthe half cycle in which trigger diode 55 is placed in a conducting stateto supply a pulse to gate 56.

As the pulse to gate 56' is delayed, the placing of switch 56 into aconducting state is similarly delayed, thereby delaying the time duringthe half-cycle in which the current is passed to the motor driving fan16, thereby reducing the speed thereof. Thus, the speed of the fan isreduced as the static pressure in the air passage is increased, therebydecreasing the flow of air through the air passage to decrease thestatic pressure therein to its predetermined level, thus tending tomaintain the discharge velocity substantially constant.

Assume now that the enclosure requires heating. Doublepole, double throwswitch 34 will be set so that arm 39 will be in contact with terminal38, and arm 40 will be in contact with terminal 36. If the temperatureof the enclosure is below the setpoint, the variable voltage controlsignal passing through resistor 25 to operational amplifier 26 will beof a magnitude to provide a negitive polarity control signal throu hline 71 to line 29. The voltage signal Wlii pass throug diode 28,

thereby energizing coil 30 and closing switch 31.

Line voltage will then pass through terminal 35. terminal 38, and arm39, to first energize coil 41. thereby causing motor 43 to rotate in acounterclockwise direction to open damper 19 as is desired to obtain agreater quantity of treated air. Wiper 46 will simultaneously move in acounter clockwise direction. Double-pole, double-throw switch 50 is setfor heating mode operation. The E, voltage signal will pass through line76, arm 51 and resistor 49 to wiper 46. The variable voltage signal thusgenerated will then pass through line 72 to resistor 54, terminating atoperational amplifier 26.

Similarly, as in the cooling mode of operation, when the damper 19 hasmoved in a counterclockwise direction, the wiper of potentiometer 60 hasmoved in a clockwise direction, thereby increasing the rate at whichcapacitor 57 is charged. As discussed before, when the charging rate ofcapacitor 57 is increased, the speed of the motor driving fan 16 is alsoincreased as is desired when the damper is moved so as to increase thedischarge area of outlet 18.

If, during heating mode operation, the temperature of the enclosurerises above the set point, the control circuit will operate to close thedamper 19 to the proper position for the required quantity of treatedwarm air.

The invention disclosed herein will pennit operation of the fan at avariable speed to supply a variable quantity of treated air inproportion to the demands of the enclosure. By regulating the speed ofthe fan as the position of the damper is varied, the static pressure inthe air passage will remain substantially constant, thereby maintainingthe discharge velocity of the treated air substantially constant as isdesired to obviate the problems hereinbefore discussed.

As is apparent to one skilled in the art, the control circuit may besuitably modified to permit simultaneous control of more than one damperbeing served by the same air conditioning apparatus.

While I have described and illustrated a preferred embodiment of myinvention, it should be understood that the invention is not limitedthereto but may be otherwise embodied within the scope of the followingclaims.

1. An air conditioning apparatus for regulating the temperature of aircirculating within an enclosure comprising a structure forming an airpassage having an outlet through which treated air is delivered to theenclosure; a heat exchanger in said passage adapted to be connected to asource of heat exchange medium for treating air flowing through saidpassage; a damper in said passage adjacent the outlet for modulating thearea of said outlet; means including a thermistor for sensing thetemperature of air in the enclosure and a variable resistance elementselectively regulable to provide a desired temperature in the enclosure,said thermistor and said element cooperating to provide a variablevoltage signal which is a function of the sensed temperature; means forreceiving said signal including means for actuating said damper inresponse to said signal to modulate the area of said outlet; a fan insaid air passage adapted to receive air from the enclosure and tocirculate the air through said heat exchanger to the enclosure throughsaid outlet; and electric motor for actuating said fan; means forsensing the change in pressure produced in said air passage by themodulation of said outlet area including means to generate a secondcontrol signal which is a function of the sensed pressure; means forenergizing said motor; means for receiving said second control signalcooperating with said energizing means to vary the speed of the motorand thus the speed of the fan as a function of the magnitude of thesignal thereby maintaining a predetermined pressure condition within theair passage to maintain the discharge of treated air into said enclosureat a substantially constant velocity irrespective of the area of saidoutlet.

1. An air conditioning apparatus for regulating the temperature of aircirculating within an enclosure comprising a structure forming an airpassage having an outlet through which treated air is delivered to theenclosure; a heat exchanger in said passage adapted to be connected to asource of heat exchange medium for treating air flowing through saidpassage; a damper in said passage adjacent the outlet for modulating thearea of said outlet; means including a thermistor for sensing thetemperature of air in the enclosure and a variable resistance elementselectively regulable to provide a desired temperature in the enclosure,said thermistor and said element cooperating to provide a variablevoltage signal which is a function of the sensed temperature; means forreceiving said signal including means for actuating said damper inresponse to said signal to modulate the area of said outlet; a fan insaid air passage adapted to receive air from the enclosure and tocirculate the air through said heat exchanger to the enclosure throughsaid outlet; and electric motor for actuating said fan; means forsensing the change in pressure produced in said air passage by themodulation of said outlet area including means to generate a secondcontrol signal which is a function of the sensed pressure; means forenergizing said motor; means for receiving said second control signalcooperating with said energizing means to vary the speed of the motorand thus the speed of the fan as a function of the magnitude of thesignal thereby maintaining a predetermined pressure condition within theair passage to maintain the discharge of treated air into said enclosureat a substantially constant velocity irrespective of the area of saidoutlet.